Year: 1984
Make: Mercedes
Model: 300TD
Engine Size: 3.0D
Refrigerant Type: R12
Ambient Temp: 98f
Pressure Low: 30
Pressure High: 235
Country of Origin: United States
I just did a conversion back to R12 on the 300TD as R134 was a struggle. System was opened flushed and the compressor flushed using the proper mineral oil. New dryer and expansion valve (stamped R134), vacuum pumped down for 2 hours in the hot sun and approx 2.6lbs of R12 from a jug per digital scales.
Vent temps are higher than expected as well as the high side pressure. Plus, the hi side pressure jumps making it difficult to read. Could this be a sign of too much oil in the system?
I had a difficult time getting the proper oil charge in the compressor and am starting to think I may have too much. I added a little here and there along the system as it was assembled.
Also, the expansion valve's "R134" calibration has me concerned.
Anyone know what happens if the system has too much oil ?
I've posted the same question here
http://www.autoacforum.com/messageview.cfm?catid=2&threadid=22261&STARTPAGE=1
Did you ever find out the answer?
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1983 Mercedes 240D on R12 and WVO!
1192 Mercedes 300D 2.5 R134a
1993 Toyota Pickup converted to R134a
If you haven't found anything, here's a good article I just found
http://www.achrnews.com/Articles/Feature_Article/c8ea088318a5a010VgnVCM100000f932a8c0____
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1983 Mercedes 240D on R12 and WVO!
1192 Mercedes 300D 2.5 R134a
1993 Toyota Pickup converted to R134a
Pd: The article you linked is in reference to HVAC, where the oils are supposed to stay in the compressor sump (note reference to oil sight tube). When these oils wash out into the heat exchangers the compressor becomes low on oil. This should not be confused with MVAC where, by design, the oils are always circulating with the refrigerant.
Dsm: The article Pd linked does state the most important and obvious problem with oil overcharge. That is the excessive coatings of oil on the inside of the heat exchangers will inhibit proper thermal transfer as designed; i.e. less heat rejection from the condenser and less heat absorption from the evaporator. This can sometimes be seen in higher than normal high and low pressures; but so can many other things can also, like residual flush for one.
Putting oil in "here and there" is not a problem as it is designed to circulate. Knowing how much is needed and installing that amount is the only way to be sure. So you stated you flushed it; verified to be clean and dry, correct? Then you put fresh oil in, this make you the only one who can know; so is it overcharged with oil or not?
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